The invention concerns an electronically commutated direct current machine having a rotor and a stator.
Electronically commutated direct current machines of this kind are known in a variety of embodiments. It has been found that they are suitable for many drive purposes, especially when their price is reasonable.
It is therefore an object of the invention to make available a new electronically commutated direct current machine.
This object is achieved, according to the invention, by providing a current limiting arrangement which is responsive to a current target value signal. Because the current limiting arrangement is adjustable by means of a current target value signal, a direct current machine of this kind is extraordinarily versatile. For example, the rotation speed can be regulated in the usual way by configuring the switching definition signal as the output signal of a rotation speed controller and regulating the rotation speed of the direct current machine using that switching definition signal, the current target value signal usually being adjusted to a fixed high value that lies at the upper limit of the current permissible for the direct current machine. In such a case, the current target value signal brings about current limitation as the motor starts up, and the value for that current limitation is adjustable in accordance with requirements, e.g. in accordance with the power level of a power supply section.
The rotation speed can, however, also be regulated in such a way that a current target value signal for the current limiting arrangement is generated as the output signal of a rotation speed controller and the rotation speed is regulated using that current target value signal, the switching definition signal being adjusted so that the current limiting arrangement is continuously active. This results in very high-quality rotation speed regulation.
Lastly, the current target value signal can also be adjusted to a constant value of a desired magnitude, and at the same time the switching definition signal can be adjusted so that the current limiting arrangement is continuously active. In this cases the direct current machine is regulated to a constant current and consequently operates at a practically constant torque, which offers considerable advantages for many applications. One of these applications is driving a radial or diagonal fan, which in combination with a constant-current control system of this kind exhibits entirely surprising characteristics.
The invention also concerns the use of a direct current machine of this kind to drive a fan, which preferably is embodied as a diagonal or radial fan. The surprising characteristics of this use are described in detail in the description below.